This invention relates to stators of canned motors suitable for use in the water and methods of producing same, and, more particularly, to a stator of a canned motor of the type in which the stator is sealed by a can, and insulator material is poured in a space around the stator.
In a motor of the type comprising a stator including a cylindrical motor housing, a stator core having a stator winding wound thereon and fixed on an inner surface of the motor housing in the central portion thereof, and a pair of end brackets each fixed to one of opposite open ends of the motor housing, and a rotor having a rotor core juxtaposed against the stator core, the rotor being located inwardly of the stator and journalled by suitable bearing means for rotation, it has been proposed to provide a canned motor having a cylindrical can located in a position inwardly of the stator. When the can is mounted inside the motor housing, the stator winding can be sealed by the can in the motor housing, so that protection of electrical components inside the motor against water can be advantageously provided for when the motor is used in the water or in high temperature atmosphere. However, no desirable effects could be achieved merely by placing a can inside the motor housing. If a can is merely attached to the inner surface of the stator, the presence of the can would cause air sealed in the stator to be expanded by the heat generated when the motor is actuated, with the result being that the expanded air would cause deformation of the can to take place. When the can is deformed, a problem arises in that the can and the rotor are brought into contact with each other. To obviate the aforesaid problem, it has been proposed to fill the motor housing with insulating material to eliminate air that might otherwise remain inside the motor housing.
Epoxy resin of high thermal deformation temperature has been used as the insulating material to be poured in the motor housing of a canned motor. Pouring of the epoxy resin has been carried out as follows: the epoxy resin, in a liquid state, is poured into the motor housing through a port formed beforehand at one of the end brackets and allowed to cure. In pouring the epoxy resin into the motor housing, the motor housing is evacuated to prevent formation of cavities on the surface of the can which might otherwise occur due to the presence of air in a space around the stator because the temperature inside the motor housing rises on account of the epoxy resin having a high viscosity at room temperature. If evacuation of the motor housing is not satisfactorily effected and cavities containing air therein are formed in the epoxy resin, the residual air would be expanded as the temperature of the stator winding rises and the pressure applied by the expanded air would increase. If this situation occurs, the can would be biased diametrically toward its center, so that the rotor located in the can might be pressed by the can and its operation might be interfered with.
Thus, in the art of pouring an epoxy resin in a liquid state into the motor housing of a canned motor and allowing same to cure, it is essential that a high vacuum be obtained inside the stator when the epoxy resin is poured therein, and the prior art has suffered the disadvantage that the operation of connecting the stator to a vacuum device and the operation of preparing for the pouring of the resin are timeconsuming. An additional disadvantage is that, since the insulating material consists of resin only, it becomes heavy in weight and high in cost.